Photo-sensitive devices are used in a variety of electronic devices. For example, an array of photo-sensitive devices can be used to form an image sensor array to be used in a digital camera. A photo-sensitive device is typically includes a light-sensing region within a semiconductor material that transfers energy from photons into electrical energy.
The light-sensing region is typically formed into a semiconductor material through an implantation process to form either a p-i-n junction or a p-n junction. The semiconductor material in which the light-sensing region is formed is usually partially made of germanium in addition to silicon. This provides various benefits to the photo-sensitive device.
The efficiency at which the photo-sensitive device operates is affected by the characteristics of the semiconductor material in which the light-sensing region is formed. When using a semiconductor crystal that is made of silicon germanium, there may be defects in the crystal due to the different lattice constants between silicon and germanium. These defects are sometimes referred to as dislocations. These defects adversely affect the efficiency at which the photo-sensitive device operates. Thus, it is desirable to reduce these defects as much as possible.